[Structural Pattern] Understanding of Flyweight Pattern

head File

//FlyweightPattern.h

#ifndef FLYWEIGHT_PATTERN_H
#define FLYWEIGHT_PATTERN_H

#include <Windows.h>
#include <iostream>
#include <map>
#include <vector>
using namespace std;

namespace FlyweightPattern
{
    typedef struct pointTag
    {
        int x;
        int y;

        pointTag () {}
        pointTag(int a, int b)
        {
            x = a;
            y = b;
        }

        bool operator <(const pointTag& other) const
        {
            if (x < other.x)
            {
                return true;
            }
            else if (x == other.x)
            {
                return y < other.y;
            }

            return false;
        }
    }POINT;

    typedef enum PieceColorTag
    {
        BLACK,
        WHITE
    }PIECECOLOR;

    class CPiece
    {
    public:
        CPiece(PIECECOLOR color);
        PIECECOLOR GetColor();

        // Set the external state
        void SetPoint(POINT point);
        POINT GetPoint();

    protected:
        // Internal state
        PIECECOLOR m_color;

        // external state
        POINT m_point;
    };

    class CGomoku : public CPiece
    {
    public:
        CGomoku(PIECECOLOR color);
    };

    class CPieceFactory
    {
    public:
        CPiece *GetPiece(PIECECOLOR color);

        ~CPieceFactory();

    private:
        vector <CPiece *> m_vecPiece;
    };

    class CChessboard
    {
    public:
        void Draw(CPiece *piece);
        void ShowAllPieces();

    private:
        map<POINT, CPiece *> m_mapPieces;
    };

    //////////////////////////////////////////////////////////////////////////
    void FlyweightPattern_Test();
}

#endif

accomplish

#include "FlyweightPattern.h"

namespace FlyweightPattern
{
    CPiece::CPiece(PIECECOLOR color)
        : m_color(color)
    {}

    PIECECOLOR CPiece::GetColor()
    {
        return m_color;
    }

    // Set the external state
    void CPiece::SetPoint(POINT point)
    {
        m_point = point;
    }

    POINT CPiece::GetPoint()
    {
        return m_point;
    }


    //////////////////////////////////////////////////////////////////////////
    CGomoku::CGomoku(PIECECOLOR color)
        : CPiece(color)
    {}


    //////////////////////////////////////////////////////////////////////////
    CPiece* CPieceFactory::GetPiece(PIECECOLOR color)
    {
        CPiece *pPiece = NULL;
        if (m_vecPiece.empty())
        {
            pPiece = new CGomoku(color);
            m_vecPiece.push_back (pPiece);
        }
        else
        {
            for (vector<CPiece *>::iterator it = m_vecPiece.begin(); it != m_vecPiece.end(); ++it)
            {
                if ((*it)->GetColor() == color)
                {
                    pPiece = *it;
                    break;
                }
            }
            if (pPiece == NULL)
            {
                pPiece = new CGomoku(color);
                m_vecPiece.push_back (pPiece);
            }
        }
        return pPiece;
    }    

    CPieceFactory::~CPieceFactory()
    {
        for (vector<CPiece *>::iterator it = m_vecPiece.begin(); it != m_vecPiece.end(); ++it)
        {
            if (*it != NULL)
            {
                delete *it;
                *it = NULL;
            }
        }
    }

    //////////////////////////////////////////////////////////////////////////
    void CChessboard::Draw(CPiece *piece)
    {
        if (WHITE == piece->GetColor())
        {
            cout<<"Draw a White"<<" at ("<<piece->GetPoint().x<<","<<piece->GetPoint().y<<")"<<endl;
        }
        else
        {
            cout<<"Draw a Black"<<" at ("<<piece->GetPoint().x<<","<<piece->GetPoint().y<<")"<<endl;
        }
        m_mapPieces.insert(pair<POINT, CPiece *>(piece->GetPoint(), piece));
    }

    void CChessboard::ShowAllPieces()
    {
        for (map<POINT, CPiece *>::iterator it = m_mapPieces.begin(); it != m_mapPieces.end(); ++it)
        {
            if (WHITE == it->second->GetColor())
            {
                cout<<"("<<it->first.x<<","<<it->first.y<<") has a White cheese."<<endl;
            }
            else
            {
                cout<<"("<<it->first.x<<","<<it->first.y<<") has a Black cheese."<<endl;
            }
        }
    }

    //////////////////////////////////////////////////////////////////////////
    void FlyweightPattern_Test()
    {
        CPieceFactory *pPieceFactory = new CPieceFactory();
        CChessboard *pCheseboard = new CChessboard();

        // The player1 get a white piece from the pieces bowl
        CPiece *pPiece = pPieceFactory->GetPiece(WHITE);
        pPiece->SetPoint(POINT(2, 3));
        pCheseboard->Draw(pPiece);

        // The player2 get a black piece from the pieces bowl
        pPiece = pPieceFactory->GetPiece(BLACK);
        pPiece->SetPoint(POINT(4, 5));
        pCheseboard->Draw(pPiece);

        // The player1 get a white piece from the pieces bowl
        pPiece = pPieceFactory->GetPiece(WHITE);
        pPiece->SetPoint(POINT(2, 4));
        pCheseboard->Draw(pPiece);

        // The player2 get a black piece from the pieces bowl
        pPiece = pPieceFactory->GetPiece(BLACK);
        pPiece->SetPoint(POINT(3, 5));
        pCheseboard->Draw(pPiece);

        /*......*/

        // Show all cheses
        cout<<"Show all cheses"<<endl;
        pCheseboard->ShowAllPieces();

        if (pCheseboard != NULL)
        {
            delete pCheseboard;
            pCheseboard = NULL;
        }
        if (pPieceFactory != NULL)
        {
            delete pPieceFactory;
            pPieceFactory = NULL;
        }
    }
}

client

#include "FlyweightPattern.h"


#include <iostream>
using namespace std;

using namespace FlyweightPattern;

void main()
{
    FlyweightPattern_Test();
}

operation result